1986 Chevy Monte Carlo 1970 Chevy 350 with a hei distributo

MONTE SS

MEMBER
1986 CHEVROLET MONTE CARLO

Engine Performance problem
1986 Chevy Monte Carlo V8 Two Wheel Drive Automatic

I bought a chevy 350 motor that has a.030 bore, factory cam, eldelbrock intake and eldelbrock 750 carb, factory head. I installed motor and i'm getting back fire in the carb and the exhaust. I check the timeing, and that's fined. I adjusted the carb but still do it. My spark plug gap is.060. I did a compression test and my # are 90-120 on all 8. My rotor is facing #1 tdc on compression side but still same problem. I got headers and dual exhaust. Some said it could be a valve problem. Pleased help me out, it's my first time on the this sight. Ps I notice on my fuel filter thats on between the lines, witch is clear is never full, always under quarter, never half or full. Help, help, help.

1 Reply

HMAC300

MECHANIC
48,601 POSTS

If it is backfiring through the exust and intake it may be a bad cam. I'd check firing order first. #1 should be at about 11:30 on like a clock 12:oo being the very front. Bring the crank and #1 up to the timing mark and see where the rotor points. Firing order s 1-8-4-3-6-5-7-2 and it fires clockwise. If it still backfires after this then the cylinder that is at 90# take teh valve cover off and see if the rocker is moving up and down like the rest. 90# is on the low side for compression. If it doesn't move like the rest there is a good chance the camshaft is worn. And needs replacing. If it is the cam, then try to lube it with either white grease and the lifters, and hen keep the engine revved about 2000 rpm for the first 2 or 3 minutes. This is the proper way to break a new cam in, especially the older small blocks. If you still have prblems private message me as I don't check my posts all the time.